import type { H3Event } from 'h3'

interface LinkValue {
  value: string | null
}

export interface ShelfBookRow {
  id: number
  title: string | null
  title_german: string | null
  authors: LinkValue[]
}

interface Field {
  name: string
  link_row_table_id?: number
}

let booksTable: string | null = null

/** The books table, taken from the wishlist table's `books` link field. */
export async function wishlistBooksTable(event: H3Event): Promise<string> {
  if (!booksTable) {
    const fields = await listFields<Field>(event, wishlistTable(event))
    const id = fields.find(field => field.name === 'books')?.link_row_table_id
    if (!id) {
      throw createError({ statusCode: 500, statusMessage: 'The wishlist table has no "books" link field' })
    }
    booksTable = String(id)
  }
  return booksTable
}

export function toShelfBook(row: ShelfBookRow): WishlistShelfBook {
  return {
    id: row.id,
    title: row.title_german?.trim() || (row.title ?? '').trim(),
    authors: (row.authors ?? []).map(({ value }) => value?.trim()).filter((value): value is string => !!value)
  }
}

/** Books from the books table matching a Baserow filter, e.g. `{ filter__read__boolean: true }` */
export async function listShelfBooks(event: H3Event, filters: Record<string, unknown>): Promise<WishlistShelfBook[]> {
  const rows = await listRows<ShelfBookRow>(event, await wishlistBooksTable(event), filters)
  return rows.map(toShelfBook).filter(book => book.title)
}